ON MOUNTING MICROSCOPICAL OBJECTS. xxxiii 



No cell is required for sections. Copper, brass, and vulcanite 

 cells are to be avoided. 



^ An object may be mounted dry by fixing it to the slide in 

 th.-centre of a cell with a very small quantity of collodion or 

 gum-water, or of solution of shellac in creasote or alcohol. 

 When the cement is dry, a cover of the same diameter as the 

 eel!" is to be laid over it, and secured by varnishing at the 

 edge with any of the cements sold for the purpose. 



, More usually it is advisable to mount an object in a liquid 

 or' solid medium. Such are glycerin, which is liquid ; 

 PiTrrant's medium, and Canada balsam, which are liquids 

 becoming solid ; and glycerin-jelly, which is solid when cold, 



,^ An object, stained or otherwise, to be mounted in glycerin 

 0/ Farrant's medium may be transferred to it direct from 

 water — great care being taken to avoid introducing air. The 

 drop of glycerin, etc., used should be just large enough to 

 spread out to the edge of the cover. When glycerin is used, 

 the cover must be fixed by means of gold size or other 

 cement apphed round the edge with a small paint-brush. 



To mount in glycerin-jelly the object is first soaked in 

 glycerin and then in melted glycerin-jelly [see Appendix) ; it 

 is then transferred to a drop of the melted glycerin-jelly upon 

 the slide, and the warm cover, previously wetted with the 

 melted jelly to aid in excluding air, is immediately placed 

 upon it and held in position till the jelly solidifies. Avoid 

 heating more than is necessary. The edges of the cover 

 may be cemented as above, but this is not absolutely necessary. 

 To mount an object in Canada balsam, it must, after 

 staining, be dehydrated by soaking in absolute alcohol ; then 

 soaked in oil of cedar- wood or xylol, till the alcohol is re- 

 moved ; and, lastly, placed in the drop of balsam upon the 

 slide and covered. 



Mounting sections cut in paraffin. Take a clean dry 

 slide and spread evenly over it with the finger a very thin 

 layer of glycerin and albumen (see Appendix), so that the 

 slide appears to be oiily slightly greasy. An excess of 

 glycerin and albumen must be avoided, otherwise the sections 

 will be cloudy. Place the sections perfectly flat upon the 



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